This application relates to a valve located adjacent to a compressor discharge line, and operable to prevent backflow of compressed refrigerant into a compressor pump unit, and the resultant reverse run of the compressor upon a compressor shutdown.
Compressors are utilized in most refrigerant compression applications. In a compressor, a refrigerant is typically brought into a suction chamber that surrounds a motor for a compressor pump unit. The suction refrigerant cools the motor, and eventually travels into the compression chambers of the compressor pump unit where it is compressed, and passes through a discharge port into a discharge chamber. From the discharge chamber, the refrigerant passes into a compressor discharge tube, and then downstream to the next component in the refrigerant system.
One common type of compressors that is becoming widely utilized is a scroll compressor. In a scroll compressor, a first scroll member has a base and a generally spiral wrap extending from the base, and a second scroll member has a base and a generally spiral wrap extending from its base. The two wraps interfit to define the compression chambers. The first scroll member is caused to orbit relative to the second scroll member, and as the two orbit relative to each other, the size of the compression chambers decreases, thus compressing the entrapped refrigerant.
Scroll compressors have a problem with an issue called unpowered reverse rotation. The scroll compressor is preferably driven to orbit in a preferred direction. If the first scroll member is caused to orbit in the opposed direction, undesirable noise and potential damage to the compressor may occur, due to over-speeding of the orbiting scroll and shaft counterweights.
At shutdown of the scroll compressor, there is a significant amount of compressed refrigerant stored in the condenser and adjacent discharge piping downstream of the compressor. Upon a shutdown, this compressed refrigerant expands through the compression chambers, and drives the orbiting scroll member in the reverse direction. This is undesirable.
Discharge check valves installed inside of the scroll compressor are sometimes utilized to block the refrigerant from expanding through the scroll elements and thus preventing the reverse rotation. The check valves may have reliability problems as they can wear and break in fatigue after prolonged operation. As such, there is a concern with regard to unpowered reverse rotation as it relates to the use of the internal check valves.
A similar problem exists with screw compressors where the refrigerant can expand through the screw compression elements, if there is no adequate means to block this reverse flow of refrigerant. The rotation of screw elements in reverse can damage the screw rotors of the screw compressor.